Why is the axis slanted?

This axial tilt is caused by the background stars. The earth faces these background stars and spins in it’s orbit. During one half of it’s orbit, the north pole faces away from the sun and during the other half, it faces toward the sun.

Even though it is tilted due to background stars, it’s axial tilt changes. Right now, it is at a tilt of about 23.4 degrees. Each century the angle decreases by about 47 inches.